Purification and extraction of sulphur bearing material



112, i936. R H. CLAYTON ET AL. l 2,@4059 PURIFICATION AND EXTRACTION OF SULPHUR BEARING MATERIAL Filed July 8, 1932 Sc/P//U/FJULL 7 u 55 56 Q2?! {ij/[58 Patented May 12, 1936 UNITED sTATEfs PATENT OFFICE PURIFICATION AND EXTRACTION OF SUL'PHUR BEARING MATERIAL Dany ApplicationvJulyS, 1932, Serial No. 621,506 In Great `Britain July 17, 1931 v11 Claims.V

This invention relates to the purification of sulphur bearing materials which .contain .eX- tractable free sulphur and organic .impurities of a tarry nature and the extraction of sulphur from such materials. Such sulphur bearing materials may be crude sulphur itself, or ,material containing sulphur such as spent -oxide which has been used for the removal .of sulphur from sulphur-bearing gases.

In the extraction of materials .containing Vextractable free sulphur .and organic impurities of a tarry nature, difficulty is experienced .in eliminating such organic impurities which tend to contaminate the sulphur. Numerous proposals have been made for purifying crude sulphur with the object of removing tarry impurities. Such processes are generally -only effective when .the proportion of the impurities is .relatively low. For example, when purifying :crude sulphur by 2O passing sulphur trioxide Athrough the molten material and then filtering the pure sulphur from the insoluble residue, it has been found that tif .a high proportion of organic impurities be present the increased amount of insoluble residue on 'the filter retains an undue proportion of sulphur.

One object of the presentinvention is to :provide an improved process Vby means of which the excessive amount of organic impurity is removed from the raw materials and the sulphur is immediately extracted in a vpurer .form which 'is more amenable to nal purification by .the above mentioned process, by distillation, or by other known methods. Another object of the invention is to provide an improved process enabling 35 sulphur of a reasonable degree Yof purity to .be extracted from crude sulphur or other sulphur bearing materials by the aid of va solvent inthe cold. A still further object is to providea process in which the tarry matters are removedfrom raw materials containing extractable free :sulphur by means of a saturated solution of sulphur in carbon bisulphide which is produced by extraction of sulphur from the 4raw materials themselves.r A still further object 'is to provide a continuous process for the Aextraction of sulphur from successive portions of the raw .lmaterial with continuous vpreliminary removal of the tarry matters by means of a portion of the solution of sulphur formed on extraction. These and other objects of the invention `will vbe apparent from the following description land fthe appended claims.

We have observed that the :tarry matter in general Aexists on the surface of the crystals or particles of the crude sulphur .or sulphur bear- (Cl. ,Z3-238) ing materials such as spent oxide and Vit vis 'not diffused throughout the sulphur in thev mass. A solution of sulphur in carbonbisulphide which may be saturated with sulphur is still capable `of removing the tar, oil or other organic impurities 5 usually associated with such raw materials and we are thereby enabled to effect substantial vremoval of the tarry matters in a preliminary op-Y eration and then extract sulphur in a purer form from the thus preliminarily treated material.

In carrying out the present invention the im pure sulphur or sulphur bearing material is. washed with a saturated solution of sulphur iin carbon bisulphide formed in situ by treating a portion of the raw material with carbon bisulphide and thereafter employing this solution on a further quantity or successively on further quantities of the raw material contained, forexample, in closed vessels with inlets and outletsY for the solvent. A plurality of vthese vessels is 20 connected in series, so that the `countercurrent principle is employed whereby Ythe carbon bisulphide flows successively through vessels containing material .progressively richer -in sul-phur, and sulphur solution flows through vessels containing tarry matter until the quantity of tarry matter contained in such solution renders lit necessary to remove it from Athe system.

In one method of working, several vessels are required some of which at any given time are in the `extraction series,others Iin the washing series, while the remainder Iare Ybeing emptied or iiIled. Each vessel is provided Yat the top with van inlet for sulphur solution or :carbon -bisulphide and a connection from `the bottom of the .preceding vessel .and at the bottom with a false bottom, anVv outlet for solution and a connection to the top of the next succeeding vessel. The inlets `at the tops of the vessels may be provided with sprays or other Vdevices to secure adeguate distribution of the sulphur solution or carbon bisulphide through the contents of the vessel.

VA preferred method of carrying out the invention will now be described in greater detail with reference to the accompanying diag-rammatic drawing in which:

Figure 1 shows four vesselsnumbered l to 4 together with pipes and valves associated therewith,. while VFigure 2 shows a set of eight vessels numbered 3| to 38 similarly connected and similarly constructed, for the purpose of illustrating the cyclic character of the operations.

5 is a carbon bisulphide storage tank, `6 fa'stlll.

forthe tarry solutions and 'l a still for the puri- 545' v2 M t Y ned stuphur solutions. It win be obvious that if 'desired either of these stills or both Vof them may be duplicated to enable the operations to be carried out continuously while either or both of the stills may .be opened for emptying. Valves I2 to 30 are provided where shown on Figure 1.

YIn this preferred form the saturated solution of sulphur in Vcarbon bisulphide, which is em# ployed for removing the tar, is produced in situ Vby feeding, carbon bisulphide or 'aidilute solution of sulphur in carbon bisulphide on to the material in theV extraction vessels.V vThisY carbon bisulphide or dilute solution of sulphurvin carbon bisulphide takes up both sulphur and tar extraction `of the sulphur. Whenthe extraction of the sulphur has proceeded so far that the solutions thereafter obtained are too dilute for Y economical recovery of sulphur therefrom, such Jacent extractors.v

dilute solution of sulphur in carbon bisulphide can be utilized for the purpose above indicated.

The flow of washing solution need only be slow,

Vwhereas the flow of extracted solution is rapid, so

thatvery much more pure sulphur solution is prof duced than is Yrequired for use in the washing `A pipe line 8 is provided for the feed of carbon Vbisulphide to one or otherof the extractors, a Y pipe line 9 for the removal of tarry solution and apipe line I0 for theremoval of sulphur solution. If the still`1and still 6 are not required to be Vconnected up to any of the extractors at the same time, it is possible to dispense with the pipe line I0 and connect the sulphur still to the pipe line .9. YValved pipes VI I 4are provided between ad- .',Ihe'crudefsulphur lto be'puried is lled into the `four vesselsY numbered one to four. Carbon bisulphide is run intdNo. I where .it first dissolves sulphur and tar. This solution when saturated with Asulphur .will continue to removetar. VThus vas-it runs from the bottom of No. I itis saturated with sulphur and contains a large quantityof tar.Y So long as the proportion of tar which it contains is `too high' to permit of ,passing it to the next vessel in the series the solution is run tothe still 6. soon as the tar contentof the solution flowing from No. I falls toy a valve permitting its use 'for further washing. the solu-i tion is fed on to the top ofY No.2.

Y 1in-turn, the tarry solution from the bottom of No.2 isrrun tothe .still 6 vforla time until the tar contentV falls below the convenient limit. 'The thus brought into the washing series and tarry solution removed from the bottom of No. 3`to therstillY until its tar content in turn falls belowy the convenient limit, when the' solution from No.

3 is'fed on to the top of No, ,4 and so on. VMean- Y. while, however, the solution is testedas it leaves No., I.

n When sufficiently free from Vtar atv this pointfthe solutionis no longer run onto the ma' terialin No.2 but is-.diverted to the still 1. Dur-V ing this operation the Vwashing solution is allowed to 'stand inves'sel 2 .and any other vessel orV vessels which may bein the washing series.V When the concentration of sulphur in the solution flowing from No.; I falls below the economical .limit .this

Aand rie-filled.

solution instead of being fed to the still 1 is again fed to No. 2.

When the liquor flowing from No.2 is in turn sufficiently free from tar it is .likewise diverted to the still 1 and when the' sulphur content of the 5 liquor flowing from No. I shows that the material therein has been practically completely exhausted the feed of carbon bisulphideis transferred to No. 2. No. I is then drained, steamed, cleaned l) There maybe three or more vessels in each Vseries at onetime if required and there may be more vesselsri'n the extracting series than in the washing series,'if it is desired to allow more complete exhaustion with a rapid flow of carbon bisull5 phide.

Referring Vnow to Figure 2 of the drawing, for

convenience only those connections actually in use .during the operations to be Vdescribed are marked While those connections about to be used 20 Y are shown in dotted lines. AIt willbe understood .that the vconnectionsishown in Figure 1 are available, e. g. the pipe lines 8, 9 and I0 and in particular ,thebttom of the vessel 38 may be connected Vto the `top of the vessel 3|. Y Thisai-, rangement will be described with referenceto the'` removal of sulphurfromspentoxide. At the time Y selected `for illustration Ao'f the cycle of operations, the vesselI 3I vhas just been emptied of extracted oxide, vessel 432 is jbeingsteamed `for removal of 30 residual adherent solvent, .vessels'33, 34 and 35 are being vextracted for sulphur, vessel 36 is lying filled with tarry solution, the greater part of the tarry material being concentrated in the lower halfof the vessel, vessel 31 is lledwithspent 35. oxide ready ifor washing and `vessel 38.is being Y filled. The Acarbon bisulphide fedto the top Yofvessel 33 flows through .vessels 34and 35 to the still 1. Y As soon as thesulphur `solution vflowing to the still 1 `falls below A.the economicall limit for sul- 470v phurrecovery the valves are manipulatedso that the;solution;flowsrfrom the. vessel 35 .to the vessel 36.

Tarrysolutioniisthen withdrawn fromthe bot- As soon as 4 5 flowing from the bottomof the vessel 31 is nfed 50,

to the still 6. f

Meanwhile, however, the solution flowing from vessel 33.is tested and as soon as it is found that thesulphur has been practicallyV completely extractedfrom the spent oxide contained therein, 55r

thesolution is blown out, e. g. by steam,into the vessel 34.and the fresh carbon bisulphide fed into the top ofthe vessel 34. 'The vessel 33 can now be steamed, to remove traces of solvent, and emptied.

Meanwhilealsothe solution flowing fromvessel 60,

36 is tested and as soon as it is sufficiently free from tar it is .fed to the still 1.A While the solution is fedto the still 1, the vessel 31 is lying Y idle lled ,with .tarry solution. 'In some cases 'it may happenV that the next vessel 38 Vwhich by then 65V has'been'lled, may have been brought'intothe Y washing seriesand in this case both the vesselsV 31 and 38 willbe lying idlellled with tarry solution..'l Y' f By continuing in this manner thel vessels 38, 3I, 70i

vessel. .'Iheoperationsmay be regarded as a suc- 7:52

cession of displacements rather 'than asa continuous iioW, the final displacement being effected by steam so as to leave the vessel empty of solvent.

For this purpose therefore it is sulilcient merely to test the liquor flowing from the vessel 33 and allow solution to ow from the vessel to the still 1 so long only as solution is being fed from vessel 33 to 34. Thus when the liquor in vessel 33 is to be displaced by steam, the vessel 35 is disconnected from the still 1 and connected to the vessel 36. The solution in vessel 35 is then displaced into vessel 36, in turn displacing a portion of the solution in vessel 36, which is more strongly tarry, into the still 6. The displacement into the vesselI 31 of the solution from vessel :36 which contains too little tar to necessitate delivering it to the still 6 but too much tar tov permit it to be delivered to the still 1 is continued untilI the vessel 31 is full. Any surplus carbon bisulphide which may remain in vessel 33 (which is of larger net liquid capacity than 31 owing to the removal of the sulphur) is dealt with in any convenient manner. Vessel 31 then stands Vidle while sulphur solution is withdrawn from the bottom of vessel 36 and. delivered to the still 1 until such time as the vessel 34 is substantially freed of sulphur.

The material recovered in the still 6 contains the greater part of the tar which was originally contained in the spent oxide. It is in fact a form of sulphur heavily contaminated with tar, containing for example 14% or thereabouts of tar.

The invention is not, of course, limited to the specic modes of operation as described above.

We declare that what we claim is:-

1. Process for the removal of impurities and the extraction of sulphur from material containing extractible free sulphur and impurities of a tarry character, which consists in first causing a saturated solution of sulphur in carbon bisulphide, which contains too much tarry matter to render it Suitable for recovery of sulphur therefrom but is still capable of taking up further tarry matter to flow through a body of said material until the greater part of the tarry matter has been removed therefrom, then causing an unsaturated solution of sulphur in carbon bisulphide substantially free from tarry matter to i'low through said material from which the greater part of the tarry matter has been removed then causing successively more dilute solutions of sulphur in carbon bisulphide all of which dilute solutions are substantially free from tarry matter to ow through said material from which the greater part of the tarry matter has been removed, and recovering sulphur from some at least of said solutions substantially free from tarry matter after they have flowed through the said material from which the greater part of the tarry matter has been removed.

2. Process as claimed in claim 1 in which neat carbon bisulphide is nally caused to ow through said material from which the greater part of the tarry matter has been removed.

3. Process as claimed in claim 1 in which some at least of said saturated solution of sulphur in carbon bisulphide after flowing through said material is caused to low through another body of material containing extractible free sulphur and impurities of a tarry character.

4. Process as claimed in claim 1 in which said saturated solution of sulphur in carbon bisulphide containing tarry matter is displaced downwardly by said unsaturated solution of sulphur in carbon bisulphide.

5. Process as claimed in claim 1 in which some at .least of 'said saturated ysolution of sulphur in carbon bisulphide containing tarry matter after contact with said material is evaporated for the recovery of carbon bisulphide and tarry sulphur.

6. Process as claimed in claim 1 in which said more dilute solutions of sulphur in carbon bisulphide displace each other successively in a downward direction from contact with said material low in tarry matter.

7. Process for the extraction of a grade of sulphurlow in tarry matter and of a grade of sulphur high in tarry matter from material containing extractible free sulphur but high in tarry Amatter which consists in rst contacting said material high in tar-ry matter with so much of a saturated solution of sulphur in carbon bisulphide which contains too much tarry matter to render it suitable for recovery of sulphur there4 from but is still capable of taking up further tarry matter as to remove a major part of the tarry matter from said material high in tarry matter, displacing said saturated solution of sulphur in carbon bisulphide thereby enriched in tarry matter from contact with said material leaving said material low in tarry matter but 'A f substantially unchanged as to its sulphur content, treating a rst portion of such displaced solution heavily contaminated with tarry matter for recovery of carbon bisulphide and of a grade of sulphurhigh in tarry matter, bringing a later portion of such displaced solution still capable of taking up tarry matter into Contact with separate further materials high in tarry matter to be treated, contacting the said material low in tarry matter from which said solution has been displaced with an unsaturated solution of sulphur in carbon bisulphide thereby extracting a grade of sulphur low in tarry matter from said material low in tarry matter, and then contacting said material low in tarry matter successively with more dilute solutions of sulphur in carbon bisulphide all of which dilute solutions are substantially free from tarry matter.

8. Process as claimed in claim 'l in which said more dilute solutions of sulphur in carbon bisulphide displace each other successively in a downward direction from contact with said material low in tarry matter.

9. Process for the extraction of a grade of sulphur low in tarry matter and of a grade of sulphur high in tarry matter from material containing extractible free sulphur but high in tarry matter which consists in rst contacting said material high in tarry matter with so much of a saturated Solution of sulphur in carbon bisulphide which contains too much tarry matter to render it suitable for recovery of sulphur therefrom but is still capable of taking up further tarry matter as to remove a major part of the tarry matter from said material high in tarry matter, displacing said saturated solution of sulphur in carbon bisulphide thereby enriched in tarry matter from contact with said material leaving said material low in tarry matter but substantially unchanged as to its sulphur content, treating a first portion of such displaced solution heavily contaminated with tarry matter for recovery of carbon bisulphide and of a grade of sulphur high in tarry matter, bringing a later portion of such displaced solution still capable of taking up tarry matter into Contact with separate further material high in tarry matter to be treated, contacting the said material low in tarry matter from which said solution has been displaced with an unsaturated solution of sulphur from tarry matter and iinally contacting said material with neat carbon bisulphde'.

10. Process for the removal of impurities and the extraction of sulphur from material containing extractible free sulphur and impurities of a tarry character which consists in confining a plu.- rality of portions of said material in separate vessels and subjecting the portion of material in each Vessel in succession to the following sequence of operations, namely, contacting said portion of material With so much of a saturated solution of sulphur in carbon bisulphide containing tarry matter in quantity suflicient to render said saturated solution unsutable for recovery of sulphur therefrom by evaporation but insuicient to render it incapable of removing tarry matter from said portion of raw material as to cause said saturated solution to take up the major part of the tarry matter/from said portion of raw material, displacing said saturated solution by means of an unsaturated solution of sulphur in carbon bisulphide substantially free from tarry matter thereby causing said unsaturated solution to take up Y sulphur from said portion of raw material, and

'thereafter continuing said displacement by means .of solutions of sulphur in carbon bisulphide suc- `of tarry matteris too high to render the solution suitable for removal of tarry'matter irom'raw material is evaporated for recovery of carbonrbisulphide and tarry sulphur, a second portion ofY displaced solution Whose content of tarry matter while insulcient to render said solution'unsuitable for removal of tarry matter fromY raw material is too high to' permit said solution to be evap-V orated for recovery of sulphur low in tarry matter is contacted with further material containing tarry matter, a third portionof displaced solution Whose content of sulphur is suflicient to enable sulphur low in'tarry matterto be rec'overed economically by evaporation is evaporated for recovery of carbon bisulphide and sulphurlovv in tarry matter, and the remaining displaced solution is contacted with further material from which tarry matter has been removed'ior the ex#v traction of sulphur therefrom. l Y l ROBERT HENRY CLAYTON. l HERBERT ERNEST WILLIAMS. HUGH BURTON AVERY. 

